Overload releasing toolholder



2 Sheets-Sheet l ZB IIIH 4 m R L N 0 mm m 1| ,fb WM n Z I Y A a ,l

l yM D. T. BROWNLEE OVERLOAD RELEASING TOOLHOLDER March 1, 1949.

Filed Aug. ll, 1947 111Bl 1 '-Pl March l, 1949. 'n D. T. BROWNLEE 2,463,083

OVERLOAD RELEASING TOOLHOLDER Filed Aug. 11, 1947 2 sheets-sheet 2 /4 Si@ 35 I a?! z2 lPatented Mar. 1, 1949 OVERLUD' RELEASING 'IiQOLHOLDERl Dalmar T.,Brownlee, Indianapolis,.lnd., assignor to Charles Drexler, indianapolis, Ind.

eppiication August 11, 1947, serial No. 767,8191

6 Claims.

This invention relates to an overload releasing tool.

The invention may be embodiedr in a tap holder, ay threading device',` a torque wrench or a screw driver, for example by inserting. in the collet a tap, a threading die, a nutsocket or screw driver blade respectively,

Herein they invention isillustrated as. oit` the tap holder type and is adaptedv for machine tapping; It eliminates tap breakageto a considera ble extent, especially for small taps. Broken small taps are obviously expensive but `more esepeciallyi they are* difficult toA remove from the hole, the cost` of removal frequently exceeding the tap cost.

Safety tapholders, in genera-l use, are of the friction clutch type which require frequent ad` jus-tment to maintain the proper torque value.

The chief object of the present invention is toA provide an.- overload releasing tool holder to avoid tool breakage andwherein the torque setting will be maintained for longl periods of use without requiring adjustment.

One feature of the present invention resides in the provision of interchangeable: Shanks for suchholder whereby the holder may be adapted for various machines.

Another feature ofi the invention residesin the combination clutch and the torque value maintaining mechanism included herein.

Still another object is to provide a dependable device for use in tapping. blind-holes in the softer metals such as cast iron and aluminum. In this case, the device is adjustedto'release. at' a torque slightly in excessof that required to turn. the tap. In the tapping machine, rotating in a. forward' direction, the tap is moved into the hole whereupon it threads its Way to the bottom of the hole. Upon striking the bottom excess resistance to tap turning is set` up, which causes the device to relea-se and the tap to stop rotating. Reversalof the machine rotation then unscrews the tap out of thev hole. By reason. of mainten nan-ce of torque setting, this device may be used Without danger of stripping the threads.

This device also maybe usedin connection with an. automatic tapping machine with a set spindle travel for blind holes. In case a shallow hole is met with, the tap stops rotating upon striking the bottom hole and the collet holder spring relieves the end pressure until'the spindle. reverses rotation and unscrews the tap out of the hole, with no damage done;

This device is particularly suitedor.` group tapping where aY number ofi'blind holes are tapped 2, simultaneously. The holes may be of di-ierent depths andthe taps of different length-s; for' iii the machine is timed forf the slowest tapping operation the other taps will:` havel reached: the bottoms of their respective holes andi` stopped; until reverse rotation occurs and unscrewsfall the taps out off their. holes.

Other objects and features will be set forth more fully hereinafter.

The full nature of theinventionwill:befunden stood from the accompanyingV drawings andi the following description and claims:

In the drawingsFig.. l isa longitudinal central sectionalv view of an .overload releasablel tool holder in socket form adapted for tap and like tool holding. purposes,4 the shank being. shown in elevation.

Fig. 2 is ani elevational view' of the shank adapter.

Fig. 2A- is av similar view of al similar and smaller shank adapter.

Fig..2B.is asimilarview of a similar andlarger adapter.

Fig. 3V is aniendview of any one of theaforesaid adapters.

Fig. 4 is an elevational view of the clutch spring etc.

Fig. 5 is a transverse Isection' taken oni line 5-5 of Fig. 1 and in the directiomo'f the: arrows.-

Fig. o is a trans-verse section taken on` line {5f-6 of Fig. 1 and in the direction. ofA tirearrowsfi Fig. '7 is auperspective'view of thetorsionspringf;

In Figs. 1 and 2, IG indicates the elongated body portion of a holder shank` connected" by neck portion II to peripheral flangeportioni I2: Thisis connected at I3 to alspline` type extension that hasl radial teeth4 I4 and? a central bore 1151 In Fig. 2--A the similar or identical partsafre designated by corresponding one hundred series numerals. In. Fig. ZL-B the similar or identical parts are designated by 4 the corresponding! two hundred series of numeral-s;V

Figs. 2, 2A an'd 2B illustrate.' but threevint'er'- changeable shank devices'y for the holder? soi that it canfbe adapted to any drilling; etc`.macliine.

AretainerA I6 has at one end an` inwardlylidirected flange I 'I to engageange lf2), H2 or 2&1 2 ItsV other en'd-isexternally vflanged at l I 8i andisam'e is reduced atv I9. This" retainer is internally threaded as at 'ZIJ andthe outer Vendlisicountersurik as at 2 I.

A tubular shell or housing-1122!'ent/"clopesv aasleeve 23 that' has a reducedwneck portionl 24'internall'y splined asat 25and externallythreade'd as at26". Thus the shank', the retainer and sleeverr are rigidly connected together although same may be detached for shank interchanging as desired or required.

The shell and sleeve are locked together by washer '21 and snap ring 28. Washer 21 mounts pin 29 which projects into a recess in the body to prevent the washer from rotating. The shell may include lubricant supply port 30 plugged as at 3|.

When the sleeve of cast iron lor semi-steel rotates in the housing of steel containing 1.5% manganese there results in the housing a glazed inner surface thus providing a very durable bearing.

Within the sleeve or'pocket forming member is arclutch spring 32. It also is of 1.5% manganese steel and is slightly larger in external diameter than the confronting sleeve, internal diameter so as to have light frictional contact therewith, This spring has several narrow turns '(5) toward the energizing end and one rapidly widening turn at the opposite end. This end is where the pressure between the clutch spring and pocket, during -clutching engagement, is by far the heaviest. This spring also attains a glazed finish. Such glazed finishes wear very slowly and retain consistent performance in months of use.

At the pressure end of and within said spring is disposed a clutch collar 33. This collar has a peripheral biased face 34 for facial contact with one end of the clutch spring. It includes a radial slot 35. It oppositely is arcuately cut away as as 36 and centrally disposed relative thereto is pin portion 31.

The shell or housing 22 is tapped at opposite sides as at 38 to take adjustable stops 39 that project inwardly into the arcuate recess 36 and are selectively engageable by pin 31 aforesaid.

In longitudinal alignment with collar 33 is a torsion spring 40 having a peripheral flight portion 4I thereon against which abuts the other end of said clutch spring. This spring has the bias face 42 on said flight and includes gap 43 adjacent which is a longitudinally coextensive tongue or key 44,

A shaft 45 is rotatably supported in the clutch collar 33 and substantially enveloped by torsion spring 40. The keyway 6 takes key 44 of said spring. The shaft includes groove 41 and takes snap ring 48 having a tongue 49 seatable in said keyway. A thrust `washer 50 is interposed between the snap ring and shank as shown.

The adjacent end 5l of said shaft is reduced and is rotatably supported in bushing 52 press fitted into bore l5 of shank iD. The other end of said shaft is enlarged laterally at 53 and the periphery is splined as at 54.

The reduced extended tubular end 55 of ho-using 22 is correspondingly splined internally as at 55 so that shaft 45 can shift longitudinally thereof. The end thereof includes groove 51 taking snap ring 58. Adjacent the other end of the spline structure is groove 59 taking snap ring 60.

Slidable in the splined extension 55 is the collet holder 6l having external splines 62 and a lceltitral bore v63 confronting shaft 45. Therein is disposed a coil spring 64, The extended forward end of the collet holder is reduced as at 65 and externally threaded as at 66 to take the collet lnut 61.

The collet includes jaws 68 and tubular end 69. This tubular end has a square bore 10 therethrough 'and externally includes a pair of diametrically disposed grooves 1I to take the in- Llf) wardly directed diametrically disposed tongues 1'2 in the bore 13 of the collet holder aforesaid. The latter has tapered throat 15. The jaws B3 have a complementary exterior taper 16. These jaws form a square socket 11 which accommodates the tap or tool.

When the cap nut 61 is threaded upon threads 66 of the collet holder the latter is forced inwardly, the cap bearing upon the end faces of the jaws. As the jaws move inward in the collet holder, the tapered or biased faces force the jaws radially inward for tool shank clamping. The tongue and grooves 12-1I insure tool, collet and collet holder unitization so far as rotation is concerned.

Since the collet holder is splined to the housing 22 at 62-56 the former assembly rotates with the housing and the latter rotates through the clutch with the shank adapter.

The operation may be briefly summarized as follows:

Power is appliedl to rotate the shank in a clockwise direction when looking at the shank end. The shank drives the pocket through the spline connection. The pocket drives the clutch spring by frictional grip, friction being initiated at the narrow end, owing to the spring being a left hand helix. The wide end of the clutch spring applies torque to the wide end of the flange of the torsion spring. The single internal spline of the torsion spring transfers torque to the shaft. The splines on the flanged end of the shaft transfer torque to the housing and finally to the collet holder, collet and tap or tool as described.

When the torque exceeds the predetermined amount, the torsion spring deflects in an unwinding direction which causes an angular lag of the shaft, housing and control collar with respect to the clutch spring and pocket. As the energising end of the clutch spring is keyed to the control collar, this angular lag winds said end of the clutch spring to smaller diameter which suppresses its frictional grip. The clutch spring, housing and tap now cease rotation.

When reverse rotation is applied to the shank, the pocket drives the clutch spring from the opposite end, the wide end now becoming the energizing end and the torque being transferred from the narrow end to the control collar and thence to the housing and the tap or tool. In reverse rotation the torsion spring is bypassed and there is no overload release.

While the invention has been illustrated and described in great detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character.

The several modifications described herein as well as others which will readily suggest themselves to persons skilled in this art, all are considered to be within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

l. A reversibly rotatable tool holder having a power applying end member, a housing rotatable relative thereto, a tool supporting mechanism slidable longitudinally in said housing, a control collar, a torsion spring coaxial therewith, an internal shaft within both and connected to the torsion spring, a clutch spring helix concentrically associated with the collar and spring, a pocket member .concentrically associated therewith, the latter being rotatable by the rst mentioned member and connected to one end of the clutch spring, the other end of the clutch spring being connected to the control collar, said shaft, housing and mechanism having a spline con nection therebetween.

2. A tool holder as defined by claim 1 wherein the pocket member terminates in a detachable retaining nut, the housing being relatively rotatable but substantially axially non-movable relatively, the power applying end member having a locking flange and a slidable relatively nonrotatable connection with the pocket member, said nut effecting detachable connection between the pocket member and power applying member for latter member substitution purposes.

3. A tool holder as dened by claim 1 wherein the shaft and rst mentioned member have con fronting adjacent ends, one being socketed and the other having an extension socket seatable for internal shaft support and alignment.

4. A tool holder as defined by claim 1 wherein the pocket member terminates in a detachable retaining nut, the housing being relatively rotatable but substantially axially non-movable relatively, the power applying end member having a locking flange and a slidable relatively non-rotatable connection with the pocket member, said nut effecting detachable connection between the pocket member and power applying member for latter member substitution purposes and the shaft and rst mentioned member have confronting adjacent ends, one being socketed and the other having an extension socket seatable for internal shaft support and alignment.

5. A tool holder as defined by claim 1 wherein the control collar is oscllatable within the housing and travel limit stops limit the extent of the relative oscillation therebetween.

6. A tool holder as dened by claim 5 wherein the stops are adjustable relative to each other for adjusting the initiation, extent and termination of the relative oscillation in opposite directions.

DALMAR T. BROWNLEE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STA'IES PATENTS Number Name Date 1,537,628 Strut May 12, 1925 1,836,471 Knight et al. Dec. 15, 1931 2,184,394 Moretti Dec. 26, 1939 

